March 28, 2024

Swimming at Green Valley Lake not recommended; microcystin levels high

The Iowa Department of Natural Resources (IDNR) has identified a hepatotoxin called microcystin toxin in Green Valley Lake near Creston in Union County.

Amanda Husband, Union County environmental specialist, said people and pets should not swim or wade in the water while these levels are high. She said fishing and boating at speeds low enough to not kick up much spray, however, are safe.

"No swimming, no direct water contact is what I would advise people," Husband said. "If you're boating and you're not splashing a bunch of water up on to yourself ... just out trolling around, that's not a problem."

Microcystin toxin is released by blue-green algae or cyanobacteria. Cyanobacterial blooms can form in warm, slow-moving waters that are rich in nutrients. They most often occur in late summer or early fall.

Both humans and animals can get microcystin poisoning from exposure to contaminated water, either by intentionally or accidentally swallowing water, by having direct skin contact (as when swimming, wading, or showering) or by breathing airborne droplets containing microcystins during boating or waterskiing. Microcystin poisoning cannot be spread from one person to another, nor from an animal to a person.

Symptoms of microcystin exposure or poisoning include:

• rash, hives or skin blisters (especially on the lips and under swimsuits)
• gastrointestinal symptoms such as stomach pain, nausea, vomiting, diarrhea, severe headaches and fever
• runny eyes and nose, cough and sore throat
• pleuritic pain, asthma-like symptoms or allergic reactions
• exposure to large amount of microcystin can cause liver damage

Symptoms may take hours or days to show up in people, but normally show up within one week after exposure.

Signs will be posted when tests exceed safe levels. If there are any questions please contact Union County Environmental Health, 641-782-7803.